swift - Cast Double? to String

Question

I'm trying to cast A double? to String.

I've tried

let price = eventDataFromPrevious.dtPrice as? String
eventPriceLabel.text = price!  + "€"

but I get this error when I get to that VC:

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

My eventDataFromPrevious object looks like this in a dump:

▿ LuxEvent.EventData #0
  - idEvent: "53"
  - dtTitle: "Anniversaire de Moon"
  - dtStartDate: "2020-4-15 20:0:0"
  - dtEndDate: "2020-4-16 5:0:0"
  ▿ dtPrice: Optional(1000.0)
    - some: 1000.0
  - dtAddress: "56, Avenue Frantz Clement, Mondorf-les-Bains, Luxembourg"
  - fiCategory: "8"
  - dtCity: ""
  - dtDescription: "Soirée déguisée, apportez tous vos chiens et chiennes, et pas besoin de capotes!"
  - dtLong: "6.27737"
  - dtLat: "49.503963"
  - dtImage: "defaultImage.jpg"

Note that I have to have dtPrice as a Double? because the price can be nil if an event is free.

Thanks for the help in advance!

标签： swift

Answer 1

你不能强制 aDouble?到 a String。最好改为使用String(describing:)，例如

let price = String(describing: eventDataFromPrevious.dtPrice ?? 0.0) // 0.0 for "free"
eventPriceLabel.text = price + "€"

这也避免了强制解包结果，因为String(describing:)返回 aString而不是 a String?。

或者，如果您想显示“免费”而不是“0.0€”，您可以执行以下操作：

if let dtPrice = eventDataFromPrevious.dtPrice {
    let price = String(describing: dtPrice)
    eventPriceLabel.text = price + "€"
} else {
    eventPriceLabel.text = "Free"
}